Every now and then I come across the same issue with Adobe Flash Player not installing on a system and no fixes, shouldn't there be some other option to view Youtube videos without Adobe? Is that the only flash player which will work?
There are two open source alternatives to the Adobe Flash Player. These are Lightspark and Gnash and both are offered in Windows versions. Gnash does not support SW10 so it cannot play modern flash files on sites like Youtube. Lightspark should play most Youtube videos but there has not been a Windows port since 0.5.3 in 2011.